Finishing lime and process of making the same



Patented May 22, 1928,

ERNEST 0. SCHNELL, OF ST. LUUIS, MISSOURI.

mama Ln ln AND rnoonss OF MAKING T E same.

. Io Drawing.

This invention relates generally to .a finishing lime and the process of making the same, plastic, hydrated fini ing line which is produced from high calcium or any other kind of limestone.

. High calcium and certain-other kinds of limestone are unfit for making high plastic, hydrated finishing lime for various reasons which are very well known, and the object of this invention is to utilize these limestones to make the desirable high plastic finishing lime. The finishing limes now on the market are made out of dolomitic. limestones exclusively, their average chemical composition' being 50 per cent CaCO and 50 per cent MgCO In burning these so called high magnesium limestones there is obtainedCaO and MgO. In the following hydration the (1:10 becomes Ca(OH) whereas the MgO remains as such. In mixing these finishing limes with water MgO, a coarse material, almost insoluble in water, swells gradually but slowly, and the result after soaking for from twelve to twenty-four hours is a lime putty of such consistencythat it can be cut out of the mortar box in large pieces, piled up inlarge pieces, piled up in the bed, and readily discharged therefrom to the mortar board. It is of such plasticity that it slides off the trowel and stays put. The easy working and far spreading qualities of these finishing limes enable the plasterer to do good and fast work with the least energy, but these finishing for from twelve to twenty-four hours to get such consistency, handling and working qualities.

All the othertypes of limestones (except the above-mentioned high magnesium limestones) are absolutely unfit for making finishing lime for the following reasons:

In burning and hydrating same there is obtained at least 80 per cent (la-(H),, and in the case of a high calcium limestone even 99.5 per cent. As soonv as these limes are mixed with water'a doughy mass is obtained, which turns very soon into a tough and,

from the standpoint of the plasterer, hopeless material, because Ca (0H),, a very fine, flour-like powder, very-soluble in water, is present to excess, and that coarse'insoluble powder MgO with its characteristic physical properties and functions is practically absent.

and more particularly to a highabsorbing alarge force the particles limes have to be'soaked This lime cannotbe handled in the prescribed manner and cannot be applied Application flied February 1, 1926. Serial No. 85,378.

with satisfactory results. It sticks to the mortar box, the shovel and the hod. It works short, it. pulls and it rolls up under the trowel. Since there is a large waste of time and labor, the plasterer-s have always rejected these limes.

So far as I am aware, no one has ever produced a finishing lime out of such types of limestones, nor has there ever been any finishing lime on the market made out of such types of limestone.

' I have discovered that by adding amounts of colloidal clays and colloidal earths (bentonites) to an amount of high calciumlimestone, or other limestone which is so constituted as to be unfit for making high plastie hydrated finishing lime, a high plastic, hydrated finishing lime may 'be produced. Ordinarily I do not include in finishing lime made in accordance-with my invention :1 protecting colloid.- However, in the event the limestone is poor in alumina. and iron oxide, I find it necessary to include organic protecting colloids.

The bentonite overcomes. the before-mentioned defects of such limes and accomplishes thesame function as the MgO in the high magnesium limes, although in a different manner. The bentoniteparticles swell gradually (though relatively rapidly),

quantity of water, and of the lime putty from each other to the utmost distribution. Every particle of the bentonite envelopes itself with a fine film of water, thus increasing the tension of the surface. The larger percentage of particles are transformed into a colloidal suspension. The result is a very high plastic lime putty of the desired con sistency with splendid working and spread- .ing qualities.

The physical state of this lime putty, produced by the addition of bentonite, is not permanent. After a short time flocculation starts.

Whereas. th NCMOH) acts in the beginningns apep'tlzing agent through its increasing the negative-hydrogen-concentration of the mass and thus prevents flocculation, it acts later, as soon as the swelling has reached its maximum and the bentonite particles. are in the highest colloidal dispersion, as a flocculating agent through its increasing positive Ca-ion concentration.

This process passes on quite slowly and depends upon many factors, for instance, the

concentration of the mass, the tem erature, and especially the presence of solu le salts in the bentonite clays, which form electrolytes that promote the flocculation. The bentonite even from different sections of the same deposit contains variable amounts of such electrolytes which, when in a larger amount present, fiocculate the dispersed colloids. As a result the particles of the lime putty are drawn into closer physical contact with each other, the mass shrinks gradually, and the plasticity will be reduced. To eliminate these reactions, which diminish the plasticity, urea is used. I have found that traces of urea act here as a true rotecting colloid and stabilize the physica state of the lime putty.

Each type of limestone re uires its particularly suitable amount of ientonite and urea according to its chemical composition, and its physical properties.

he applicant adds colloidal clay of the hentonite type to a high calcium hydrated lime or to any other type of hydrated lime, which is so constituted as to be unfit for making finishing lime, for the purpose of making desirable finishing lime with its well characterized physical properties, as

plasticity, consistency, easy handling and working and far-spreading qualities.

In producing my improved finishing lime the limestone is burned just as its chemical composition requires, care being taken that said limestone is not over burned. The pow- ,de-red limestone is then hydrated with per cent emulsion of colloidal clay and earth in water. When the fresh hydrated lime has cooled to about 100 F. a 3 per cent mixture of dry colloidal clay and earth (300 mesh fine) is added thereto, after which the lime is cooled, dried, milled and blended.

In cases where the limestone is poor in alumina and iron oxide traces of urea are added as a protecting colloid.

By my method herein described I utilize all the types of limestones which could not previously be used for making finishin lime, and by so doing I produce a big plastic finishing lime of even a higher grade of plasticity and workability than the high magnesium finishing limes which are now exclusively on the market. All the finishing limes made by my process can be used immediately after being thoroughly wetted. It is not, necessary to soak them as is the case with the present high magnesium finishing lime. At the option of the workman if he so prefers the finishing lime made according to my process can be soaked in the customary manner.

I claim: V

1. The method of making a high plastic finishing lime which comprises burning the limestone, hydrating the powdered limestone with an emulsion of colloidal clay and earth in water and adding to the fresh hydrated lime when cooled an amount of a dry mixture of colloidal clay and earth.

,2. The method of making a high plastic finishing lime which comprises burning the limestone hydrating the powdered limestone with a per cent emulsion of colloidal clay and earth in water and adding to the fresh hydrated lime when cooled to about 100 F. a 3 per cent dry mixture of colloidal clay and earth.

3. The method of making a high plastic finishing lime which comprises burning the limestone, hydrating the powdered limestone with a per cent emulsion of colloidal clay 1 and earth in water adding to the fresh hydrated lime when cooled'to about F.

a 3 per cent dry mixture of colloidal clay and earth, and adding a protecting colloid.

4. The method of making a high plastic finishing lime which comprises burning the limestone, hydrating the powdered limestone with a @per cent emulsion of colloidal cla and earth in water, adding to the free hydrated lime when' cooled to about 100 F. a 3 per mnt,,.dry"mixture of colloidal clay and earthiand adding traces of urea as a protecting colloid.

In testimony that I claim the foregoing I ature.

hereunto aflix my si ER ST 0. SGHNELL. 

